The continuing aim of this research program is to explore the relations between environmental variables and the effects of drugs on behavior. The primary method of research is to develop repeatedly reproducible stable behavioral performances in experimnetal subjects using the techniques of operant conditioning and then to investigate dose-effect relations for representative drugs on these performances. Different schedules of reinforcement produce characteristically different performances that are selectively modified by other interventions. Not only do different drugs affect the same performance in different ways, but the effect of a particular drug has been found to change drastically under different schedule conditions. The conception has gradually emerged that the temporal patterning of schedule-controlled behavior is itself of fundamental importance in understanding how drugs modify behavior. Three specific lines of work will be followed: 1) To determine quantitative relations between control rate of responding and the effects of representative drugs in various species. 2) To study the effects of age and of early exposure to drugs and other experiences on the behavioral effects of amphetamines on endurance and on the related cardiovascular functioning in the rhesus monkey.